Synthesis and evaluation of grafted copolymer shrinkage-reducing admixture

Title: Synthesis and evaluation of grafted copolymer shrinkage-reducing admixture
Author(s): Gao nanxiao, Zhang jiangang, Ran qianping, Miao changwen, Liu jiaping
Paper category : conference
Book title: International RILEM Conference on Advances in Construction Materials Through Science and Engineering
Editor(s): Christopher Leung and K.T. WAN
ISBN: 978-2-35158-116-2
e-ISBN: 978-2-35158-117-9
Publisher: RILEM Publications SARL
Publication year: 2011
Pages: 317 - 326
Total Pages: 10
Nb references: 07
Language: English

Abstract: Early plastic shrinkage, dry shrinkage, and autogenous shrinkage of concrete result in cracks without any loading, and thus seriously endanger the integrity and durability of the buildings. Shrinkage-reducing admixtures have been developed and used to lessen the shrinkage of concrete. However, conventional polyether shrinkage-reducing admixtures (PSRA) not only decrease the shrinkage but also reduce compressive strength and elasticity modulus of concrete. In order to solve those drawbacks, a new grafted copolymer shrinkage-reducing admixture was designed and synthesized. In this paper, different structures of alcohols which contain unsaturated double bonds were used as initiators to synthesis the polyether macromonomer with the same molecular weights of 2400, and then the radical copolymerization was reacted between polyether macromonomer and acrylic acid(AA) to synthesis copolymer shrinkage-reducing admixture(CSRA) under different ratios. Compared to the polyether shrinkage-reducing admixture(PSRA), CSRA contributed to high water solubility. Results indicated that CSRA were effective in reducing the shrinkage of concrete in a lower dosage, on the basis of not affecting other properties of concrete. From the CSRA synthesized, the RPM(B24)-AA had the most optimal shrinkage-reducing effect and the optimal synthesize parameter was 1:1. It reduced the dry shrinkage of hardened cement paste at 28 days by about 25% when compared with PSRA by about 20% with 1% dosage. Also, it reduced the autogenous shrinkage of hardened cement paste at 28 days by about 19% when compared with PSRA by about 9% with 0.5% dosage. CSRA doesn’t affect the compressive strength and gas content of the concrete, and is compatible with some superplasticizers.

Online publication: 2011-10-31
Publication type : full_text
Public price (Euros): 0.00